Having a second look I see the problem

You don't need the call to run_ssh.

This should work for you

#!/usr/bin/perl

use strict;
use warnings;
use Net::SSH::Expect;
use lib ('./subs');
use subs;

my $ssh = Net::SSH::Expect->new (
        host => '10.77.6.55',
        password => 'mypass',
        user => 'root',
        debug => 1,
        raw_pty => 1
);

my $login_output = $ssh->login();
if ($login_output !~ /Last login/) {
        die "Login Failed\n";
}

$ssh->exec("stty raw -echo");

print "Running ls -l\n";
my $ls = $ssh->exec("ls -l /");
print "ls = $ls";

$ssh->close();
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